Lycopene, which is an important kind of carotenoid substance, has a unique long chain molecular structure and possesses more unsaturated double bonds than other carotenoids. Due to its special structure, lycopene has antioxidant capacity and ability to eliminate free radicals. The antioxidation effect of lycopene is two times of β-carotene and 100 times of vitamin E. The healthcare functions of lycopene cover many aspects, such as anti-aging, preventing cancer, enhancing immunity, cosmetic effect, and anti-ultraviolet radiation etc. It is becoming a new research hotspot in health food, cosmetics and medical fields.
China is one of the main countries planting tomatoes, tomato in China accounts for about 20% of the global yield, which is mainly planted in Xinjiang, Gansu and Inner Mongolia. Most of tomatoes in China are used for manufacturing processed tomato including tomato paste, tomato juice and concentrated tomato pulp. The by-product in the manufacturing process, tomato pomace, is generally treated as wastes and thrown away, while there exist a lot of available carotenoids in the tomato pomace, especially lycopene. Therefore, it is a topic worth thorough discussion about how to make use of tomato pomace.
European Patent EP 1103579 discloses a method of extracting lycopene, including washing tomatoes, tomato pomace etc. with low content of hot ethanol to remove the impurities and water, and then using high content of hot ethanol to extract lycopene. Although this extraction process is relatively simple, it leads to low yield of lycopene due to very low solubility of lycopene in ethanol.
U.S. Pat. No. 5,837,311 discloses a process of obtaining oleoresin containing lycopene, including crushing tomato as raw material, pulping extracting with solvent and other processes. This process uses tomatoes as raw material without the treatment of dehydration, resulting in a low yield; a large amount of solvent is needed in this process, resulting in high cost and making large scale production unsuitable.
Chinese Patent Application Publication No. CN101449801A discloses tomato skins are taken as raw material, followed by crushing the material with colloid grinder, then dehydrating with ethanol and extracting with organic solvent to produce lycopene. In this process, since the wet tomato skins containing high amount of water need to be washed and the crush capability of the colloid grinder is limited, large scale production is subjected to restriction.
Chinese Patent Application Publication Nos. CN1799674, CN1334328A and CN101298618A respectively disclose processes for extracting extracting lycopene, including using tomato skins as raw material and applying supercritical carbon dioxide extraction. The use of supercritical extraction device increases the cost and affects the industrial scale of producing lycopene from the raw material of tomato skins.
Chinese Patent Application Publication No. CN101121631A discloses that tomatoes and tomato pomace are taken as raw materials, and extracted by using ultra-sound/microwave synergistic technology associated with solvent to obtain lycopene. Although the yield of lycopene may be relatively high using this process, it cannot be used in large scale industrial production due to use of ultra-sound/microwave technology, resulting in less practicability.